In Mexico you can buy pepitas in most supermarkets. If you live anywhere else in the world, you probably have to make these yourself. Which is not a big deal (and probably a lot healthier, too). I regularly make a big batch and keep them as a staple. I love to sprinkle them onto my salad or soup and top my avocado bread with it.
Place a dry skillet over medium heat. Add only enough seeds to cover the bottom of the pan. Toast the seeds for a few minutes, giving the pan a shake every so often. Keep the seeds on the heat until golden brown and mostly puffed up.
Once done, place the seeds into a bowl to cool down. If you want to add anything else, like oil, salt and/ or spices, now is the time to do so.